1. Field of the Invention
The present invention, in general, relates to power tools and, more particularly, to an accessory for use with a table saw.
Table saws are well known tools used for cutting wood. They are used by homeowner and professional woodworker alike. All table saws have a blade on an arbor that is adapted to be raised for cutting boards at various heights or lowered below a throat plate.
The throat plate fits into a generally universally-sized elongated slot, sometimes referred to as a “throat” that is recessed in the top surface of the table saw. When installed, the top surface of the throat plate is flush with the top surface of the table saw.
The throat plate itself includes an opening for the blade to enter so that it may be extended to a position that is above the table saw surface. However, because many different types of saw blades, including wider dado blades can be used with the table saw, the opening that is provided in the throat plate by the table saw manufacturer must be large enough to accommodate the expected range of saw blade sizes.
When cutting boards on a table saw, it is preferable that the opening in the throat plate be as close to the size of the blade that is in the table saw as is possible. A precision opening that ideally is only a few thousandths of an inch larger than the saw blade decreases the amount of area intermediate the saw blade and the surrounding surface of the throat plate.
When a board is being cut, a small opening between the throat plate and the saw blade provides for optimum stability of the board. A small opening helps prevent tilting of the board that is being cut as it passes near the blade. It also helps prevent a possible snagging (i.e., resistance) of the board by the rear of the opening in the throat plate. This can occur if contact of the board with a rear portion of a large opening in the throat plate were to occur.
To solve this general need, after-market throat plates have been designed that include a replaceable center portion that fits in an enlarged central opening that is provided in the throat plate. The replaceable center portion is cut by initially raising the saw blade a desired amount. The resultant opening produced exceeds the size of the saw blade by the kerf of the blade, a very small amount. This is especially desirable.
However, current after-market throat plates have certain limitations. The replacement throat plate is not securely attached to the elongated slot provided in the top surface of the table saw into which it fits. The only known method of securement includes spring loaded detents that permit the after-market throat plate to easily be dislodged from the elongated slot. This is potentially dangerous.
Also, the replaceable center portion is not securely held in position within the replacement throat plate. Movement of the replaceable center portion can cause increased erosion (by the saw blade) which increases the size of the opening. It also allows for unwanted and unpredictable contact between the saw blade and the replaceable center portion. This can produce sudden unexpected sounds that can disturb a user.
There is also a danger that the replaceable center portion can be ejected, possibly at high speed, from the after-market throat plate. If two things go wrong at the same time a potentially serious situation can arise. For example, if the throat plate should become dislodged during use this could cause the replacement center portion to make contact with the blade. The replacement center portion can then be ejected forward, impelled by energy and speed imparted by the spinning blade. The replacement center portion can then become a projectile, possibly striking the operator. This is an extremely dangerous, possibly even a fatal scenario that is especially important to avoid.
Also, a device known as a “splitter” in the woodworking arts is sometimes included as part of a factory produced table saw throat plate by the manufacturer. The splitter is a protrusion that is located on the rear of the throat plate.
The splitter is in alignment with the plane of a standard-width type of a saw blade, one that is intended typically to rip the board lengthwise. The splitter can also be used with a blade that is intended to make a “cross-cut” in the board but its benefits are less important when a shorter type of a cut is being made. Whenever one is cutting a board, typically, as narrow a width for the saw blade as is possible is preferred (to avoid excessive waste of the board).
The splitter generally matches the width of the saw blade. It may be slightly narrower but it is not generally wider than the width of the blade. The splitter is intended to enter into the space where the cut is occurring at a predetermined distance after the blade. The splitter then holds the two cut halves apart, which prevents the board segments that have been cut from coming together and possibly “pinching” the saw blade.
Pinching can produce an irregular cut (at best) or cause binding of the blade or possibly even a burning of the board. It also subjects the cut board to unstable irregular forces that are imparted by the saw blade. In particular, a force vector tending to raise the board off of the table saw surface (as a rear of the saw blade that is most likely to be contacted during pinching is rising up from the surface) is imparted to the board when it is being pinched from the rear of the blade.
Therefore, a splitter is a desirable safety device to be included in a throat plate and many woodworkers accordingly prefer the presence of one. However, including one in an after-market throat plate has not hereto before been possible because of variation in the plane of the blade with respect to the throat plate occurring from one manufacturer to another and possibly even from one model to another produced by the same manufacturer.
Therefore, after market throat plates for table saws with a splitter are unavailable.
Accordingly, there exists today a need for a throat insert for a table saw that helps ameliorate the above-mentioned difficulties.
Clearly, such an apparatus would be a useful and desirable device.
2. Description of Prior Art
Replacement throat insert plates are, in general, known. For example, the following patent describes one such type of device:
U.S. Pat. No. 5,159,864 to Wedemeyer et al, Nov. 3, 1992.
While the structural arrangement of the above described device, at first appearance, has similarities with the present invention, it differs in material respects. These differences, which will be described in more detail hereinafter, are essential for the effective use of the invention and which admit of the advantages that are not available with the prior device.